Ceboruco hazard map: part I - definition of hazard scenarios based on the eruptive history

Abstract

Of the 48 volcanoes in Mexico listed as potentially active by the National Center for Disaster Prevention (CENAPRED), Ceboruco, located in the western Trans-Mexican Volcanic Belt, is considered among the 5 most hazardous. Its recent eruptive history includes a large magnitude Plinian (VEI 6) eruption~1000 years ago and the historical 1870-1875 vulcanian (VEI 3) eruption, as well as recent fumarolic and seismic activity. Ceboruco is a relatively young (< 400,000 years) stratovolcano characterized by abrupt changes in eruptive behavior. Individual eruptive episodes have great variations in style (effusive andesitic to highly-explosive rhyodacitic) and duration. These factors complicate hazard assessment. Three main eruptive scenarios of different magnitudes (large, intermediate, small) and eruption characteristics (likelihood of occurrence: high, medium, small) have been identified and will be presented as a background to build the volcanic hazard map for Ceboruco volcano (presented in part II of this work). Here, we report on the detailed eruptive history, with emphasis on the volcanic products of each of the eruptions, in order to identify those deposits that can serve as a reference for calibrating the modeling software (Tephra2 and Hazmap for ash fallout, Eject! code for ballistics, Etna Lava Flow Model for lava flows, Titan2D for pyroclastic density currents, and Flo-2D and LaharZ for lahars) that will be used in further steps to simulate different volcanic phenomena and lead to the construction of the hazard map.

Ceboruco hazard map: part II—modeling volcanic phenomena and construction of the general hazard map

“…The HAZMAP code was used for simulating ash falls for all three scenarios (with the restrictions of the assumption of sustained eruptive columns, which is not always the case in these smaller magnitude scenarios) and additionally the Tephra2 code was used for simulating the scenario of a Plinian eruption (scenario 3) based on the reproduction of Ceboruco's Jala eruption (see Sieron et al 2019, Part 1, for details).…”

“…The scenarios 1 and 2 were only simulated with the HAZMAP software (Macedonio et al 2005;Pfeiffer et al 2005;Macedonio and Costa 2014), using the granulometric distribution of the AD 1870 ash fallout for both scenarios, and considering a total erupted mass of 5 × 10 8 kg for the scenario 1 and 1 × 10 10 kg for the scenario 2 (details in Sieron et al 2019, Part 1), eruptive column heights of 5 km and 13 km, respectively, and using the data of monthly average wind direction and speed for these altitudes, obtaining 12 monthly ash deposit distribution maps for each scenario.…”

“…This flow, 8.2 km long and maximally 1.2 km wide, has its origin at the top of the SW slope of Ceboruco, covering an area of 5.3 km 2 . Sieron ( 2009) estimated a volume of 0.16 km 3 for the Ceboruco lava flow, recalculated later to be 0.1 km 3 (Sieron et al 2019, Part 1; Table 2). For scenario 2, the AD 1870 eruption dacitic lava flow (Fig.…”

“…Pyroclastic flow-and-surge deposits were identified in the stratigraphic record of Ceboruco volcano (Sieron et al 2019, Part 1), and it was established that concentrated and dilute PDCs could be generated in the case of explosive Vulcanian (scenario 2) or Plinian (scenario 3) eruptions (Table 2). The initial conditions under which pyroclastic flows originate have been assumed to be collapse of the eruptive column in no-wind conditions.…”

“…To delineate the areas that could be affected by surges, the perimeter of the areas indicated as affected by pyroclastic flows in each scenario was considered as the minimum limit. To obtain the maximum limit, simulations were carried out with different values of the Heim coefficient (H/L), trying to reproduce the extension of the reference pyroclastic deposits (Sieron et al 2019, Part 1; Table 2): S3 for the case of scenario 2 and S2 for scenario 3, both from the depositional sequence of the Jala Plinian eruption. For these simulations, a digital elevation model of 20 m resolution was used (INEGI 2017).…”